A pressurized package conventionally consists of a container, usually a metal can, which contains a product to be dispensed and a propellant and further includes a valve for controlling the flow of the product to be dispensed by the propellant. The pressurized container typically has the propellant supplied thereto by one of two methods.
The first method is the under-the-valve-cup method. The under-the-valve-cup method supplies the propellant to the container before the mounting cup is affixed to the container. This method generally has known drawbacks and shortcomings with the major disadvantage of the under-the-valve-cup method being that it typically has a great loss of the propellant in comparison to the second method, i.e. the pressure filling method. In recent years, there has been a significant trend toward the pressure filling method for filling cans or containers. Currently, a majority of the billions of aerosol containers, which are filled yearly, utilize the pressure filling method.
According to the pressure filling method, the propellant is filled through the valve and then a spray button is subsequently installed on the valve. Alternatively, the container can be filled or charged with the spray button already installed on the valve.
The later pressure filling method is historically known as the button-on-filling (BOF) method. The advantage of the BOF method is that the purchaser of the valves is able to eliminate the step of installing the spray button on the valve, during the production operation, as it has already been previously installed by the valve assembly manufacturer.
One major difficulty encountered in pressurizing a container is achieving a sufficient seal between the filling or charging head, the actuator or spray button and the valve/mounting cup. Past designs employed a special sealing configuration located on the skirt of the spray button adjacent the top surface of the mounting cup. The pressure required for efficiently filling a container can reach as high as 60 atmospheres (900 psig). To compensate for such high pressures, the spray button recently has been made of a relatively soft material, such as polyethylene, in order to facilitate achieving a suitable seal between the spray button and the top portion of the mounting cup. The need to achieve an improved seal, during pressurization, is more important now because the pressurizing gas has been changed, in most manufacturing methods, from chlorofluorocarbon (CFC) to hydrocarbons, which are flammable.
One drawback associated with using a softer material to manufacture the spray button is that the softer material has forced a compromise with respect to other functional aspects and considerations of the valve assembly. The softer material requires that a thicker walled, heavier spray actuator be molded at slower production rates and at higher production costs. The use of the softer material also increases the cost of the spray buttons and the costs of the injection mold design and construction as well as maintenance of the injection mold.
Despite various past efforts, directed at providing an adequate seal between the spray button and the mounting cup, it is still frequently necessary, during pressurization of a container, to increase the downward force of the filling or charging head to seal properly the spray button with respect to the mounting cup. The resulting shortcoming is that the increased load may cause the mounting cup to be depressed excessively, thereby resulting in permanent deformation of the mounting cup. The excessive depression of the mounting cup pedestal may, in turn, produce unwanted side effects, e.g. leakage of the valve, etc.